Suppose That the Amount of Time Teenagers Spend on the Internet

Suppose that the amount of time teenagers spend on the Internet is normally distributed, with a standard deviation of 1.5 hours. A sample of 100 teenagers is selected at random, and the sample mean is computed as 6.5 hours.
What happens to the width of the confidence interval estimate when each of the following things happens?
a. The confidence level increases.
b. The confidence level decreases.
c. The sample size increases.
d. The sample size decreases.
e. The value of the population standard deviation increases.
f. The value of the population standard deviation decreases.
g. The value of the sample mean increases.
h. The value of the sample mean decreases.